1. Field of the Invention
The present invention relates to a gear synchronizer mechanism adapted for use in power transmissions, and more particularly to a gear synchronizer mechanism of the type which comprises a gear member rotatably mounted on a transmission shaft, a hub member arranged adjacent the gear member and fixed to the transmission shaft for rotation therewith, a spline piece mounted on a hub portion of the gear member for rotation therewith and being formed at one side thereof with a conical portion and thereon with external spline teeth, a synchronizer ring axially movably mounted on the conical portion of the spline piece for frictional engagement therewith, a clutch sleeve encircling the hub member and having internal spline teeth in continual engagement with external spline teeth of the hub member, the clutch sleeve being axially shiftable to be engaged at the internal spline teeth thereof with the external spline teeth of the spline piece, and a thrust mechanism for thrusting the synchronizer ring toward the spline piece in shifting operation of the clutch sleeve toward the gear member to effect the frictional engagement between the synchronizer ring and the spline piece.
2. Discussion of the Background
A conventional gear synchronizer mechanism as described above is well known as a Borg-Warner type synchronizer mechanism, in which the thrust mechanism comprises a plurality of circumferentially spaced strut keys each having a raised portion in engagement with the corresponding recess in the inner peripheral wall of the clutch sleeve, and an annular retainer spring arranged to bias the strut keys radially outwardly for engagement with the clutch sleeve. To reduce the component parts of the thrust mechanism, an improved thrust mechanism has been proposed in Japanese Early Patent Publications Nos. 55-100428, 58-137627, 58-163829, and 58-174724, wherein the strut keys and retainer spring are replaced with a single thrust element. It is, however, difficult to enhance productivity of the gear synchronizer mechanism at a low cost because the single thrust element is complicated in its configuration and construction.
To overcome the shortcomings of such a conventional thrust mechanism as described above, an improved gear synchronizer mechanism has been proposed by the inventors in copending U.S. patent application Ser. No. 791,947, filed on Oct. 28, 1985, now U.S. Pat. No. 4,674,614, wherein the clutch sleeve is formed at its inner periphery with circumferentially equi-spaced three internal radial projections which are disposed within circumferentially equi-spaced three axial grooves formed in an outer cylindrical portion of the hub member, and wherein the thrust mechanism comprises a radially contractible C-letter shaped spring supported in place by engagement with circumferentially spaced inner walls of the outer cylindrical portion of the hub member, the C-letter shaped spring being formed at opposite ends thereof with a pair of circumferentially spaced axial legs and at an intermediate portion thereof with an axial leg, the axial legs each extending from the spring toward the respective internal radial projections of the clutch sleeve and having a radial projection arranged to be brought into engagement with each of the internal radial projections of the clutch sleeve and arranged to abut against the syhchronizer ring and thrust the same toward the spline piece.
In the above-described synchronizer mechanism, however, the pair of circumferentially spaced axial legs of the C-letter shaped spring each are located within the corresponding axial groove formed in the outer cylindrical portion of the hub member. In this arrangement, the opposite ends of the C-letter shaped spring are free to move radially inwardly in the respective axial grooves and tend to remain in their displaced positions. If the axial legs of the spring may not be retained in their correct positions for engagement with the internal radial projections of the clutch sleeve, insufficient balk action of the synchronizer ring will cause undesired gear noises in shifting operation of the clutch sleeve toward the gear member.